Energy demands are an ongoing problem in the United States and world-wide. As a result of these energy demands, new sources of energy and sources of more efficient harnessing of energy are needed. Systems for providing new sources of energy and more efficient methods of harnessing energy relating to coal may meet the energy demands.
Due to slower overall combustion kinetics, excess oxygen requirements for coal combustion and other solid fuel combustion are generally much higher than for gaseous and liquid fuels. For example, whereas the stoichiometric ratio (i.e. ratio of actual to theoretical minimum O2 required) for gas combustion is often 1.05 (5% excess) or less, the stoichiometric ratio for coal combustion is more typically in the vicinity of 1.2 (20% excess). While operating with a higher stoichiometric ratio, air-coal combustion results in higher fan power requirements (typically a fraction of a percent of gross power generation of the steam turbine) and stack sensible enthalpy losses. As such, the efficiency of oxy/coal combustion is much lower (typically of the order of several percent of gross generation).
The combustion of coal for power boilers is typically performed using air as the oxidant. As CO2 sequestration becomes more prevalent and legislation and regulations require sequestration for coal fired plants, the use of synthetic air with a high concentration of O2 (i.e. oxygen volumetric concentration >35%) and substantially pure O2 as the oxidant will become more desirable due to the increased concentration of CO2 in the flue gas stream of oxy/coal combustion systems. However, the combustion process of coal in high O2 concentration synthetic air and substantially pure O2 (referred to collectively as oxy/coal combustion) is different than coal combustion in air (referred to as air/coal combustion). Oxy/coal combustion is different than air/coal combustion because oxy/coal combustion typically has a higher flame temperature and different flame momentum. These differences become especially important for retrofit installations because the oxy/coal flame must fit within the existing firebox. Additionally, as the oxygen concentration in the oxidant for oxy/coal combustion increases, the flame temperature and concentration of slag forming components in the furnace also increases.
Therefore, there is an unmet need to provide components and systems for oxy/coal combustion to provide increased contact time between oxygen and coal to provide desirable combustion properties.